Someone mentioned that on the last page, and I responded. TL;DR of it is I feel like it's much more useful and aesthetically pleasing for iron bars than glass panes, and stained glass feature parity would drive needed blockstates for this up the wall without much benefit. Sure, you can't get a good glass box either, but that's also not as much of a thing, and glass blocks already serve as a transparent glass floor.... whereas iron doesn't have that and is also more resistant to mining and explosions.

Yeah now that you mention it the stained glass would be a nightmare haha.

In the first 1.9 snapshot, 15w31a, the Ender dragon battle was changed a bit with iron cages put around ender crystals, composed like this:

I think it's somewhat odd, and doesn't really achieve the cage look (also, you can fall through the top). Now to fix this, instead of making iron bars connect horizontally, I suggest a new block, the iron grate, should be placed on top of these structures (without iron bars attempting to make a top):

(ignore the black spots, those are caused by me using stairs and rendering errors)

It would give 3 iron grates when crafted.... possibly reversible (either just by putting it in the crafting grid, or 3 iron grates places in a vertical line in the crafting grid)

or even the recipe could just be a toggle... just placing it in the crafting grid switches between iron bars and an iron grate, which would allow freely switching between vertical and horizontal without a crafting table.

Naturally generated?

Yes. In the End on ender crystal cages. Possibly in strongholds, either as rare sections or possibly to fill holes in the floor. Possibly even in villages.

Technical details:

The block is 2px tall, and X/Z size depends on what state (can be a full X/Z square, half of one, or 1/4th). Outer connection is very similar to how stairs connect.

Blockstate consists of half (can be top or bottom), north/south/east/west (which can be false or true) and shape (full, line, inner, outer). (Well, I'm not sure on the best way to do this)

Models:

all sides being false/true will result in a full shape

two (adjacent full) or three (adjacent full/opposite line) adjacent or opposite blocks being filled with result in the middle being full (plus line being converted to full shape)

one sides being true will result in a "line" shape (1/2 block)

two adjacent sides being line shapes will cause the middle to be a corner shape, either inner or outer

top/bottom don't connect

So: 1 full model, 1 line model (4 rotations), 1 corner model (4 rotations). Top+bottom= 6 models, roughly 19 blockstates? Possibly better state configuration, connecting a corner to another side (turning it into a line) seems like an odd idea that adds complexity and some state maybe...

Other uses:

In addition to the vanilla iron cage, the lower half can be used as grating over floors, or as a decoration for lights embedded in ceilings.

While the upper half can be used as flooring, either alone or flush with regular flooring. It could also be used as an iron mesh just below ceilings.

TL;DR: a slab-like incarnation of iron bars useful in vanilla structures, sci-fi/industrial/evil lair environments. Also sort of like a blast resistive carpet. Good as a flooring that allows you to see (with slight obstruction) below/above without it being easy to break like glass (plus, better aesthetics).

If anyone would like to post this to /r/minecraftsuggestions to increase the chance that mojang might see it, feel free encouraged to do so. Text, pictures and all.

Oh yes, we need this! I can make up a few more models to demonstrate the connecting types.

edit: models are going to be a little more complex than I thought -- a single block can't encompass all the combinations. But it will work something like CTM.

I think I've discovered a better way to do it... the new block itself could just be oriented to the top or bottom, and then when placed next to iron bars like this:

The iron bars would use a different model for those 8 combos (on the top half, 8 more for the bottom) and the good thing is that it could be used on multiple layers properly versus just on the top and bottom if you used connection on the iron grate itself. (I edited the OP with some of this info)

ARG, that only works in a perfect world where the user doesn't try to place the iron bars in different ways... However, maybe multi-part could fix that?

Rollback Post to RevisionRollBack

"I'm an outsider by choice, but not truly.
It’s the unpleasantness of the system that keeps me out.
I’d rather be in, in a good system. That’s where my discontent comes from:
being forced to choose to stay outside.
My advice: Just keep movin’ straight ahead.
Every now and then you find yourself in a different place."
-George Carlin

For one, it wouldn't fit in with iron bars. In resource packs and even default, iron trapdoors look good as trapdoors but not really as floors. Trapdoors are also much thicker than what I'm suggesting, so it wouldn't mesh well with iron bars and wouldn't fit in like my previous comment/alternate blockstate setup where iron bars connects to it. Also making trapdoors that obstruct view (like for traps in maps/games... because they are opened by redstone, or just because they should feel "secure") would conflict with trying to match iron bars' airier style. Basically it wouldn't look good on player cages or the end pillars because it is obviously a different theme/purpose.

Grates would also be dedicated floor/ceiling.... any redstone placed would not risk opening your platforms into a state that can only be fixed by removing the redstone. The upper half of a grate would also act like an upper slab: torches, redstone, doors, etc. (basically anything you can place on a normal block) would be supported.... whereas upper trapdoors don't support any of those.

Even if you made iron bars connect to trapdoors as a ceiling/floor and made it 2px tall with an iron bars-like texture AND made the top half usable as normal floor (like blocks with torches etc.) with the inability to open if not properly hinged to a solid block: you're only leaving out a slab (that doesn't even have a double version)... which I'd imagine modifying the trapdoor to behave like that would be more work (and more drawbacks) than doing the block directly.... and you don't gain anything out of it, really.

TL;DR:

Plus, That change also seems kinda unreal to me... I get that they shouldn't need support if they're on the ground... but having them in midair and they still open and everything is weird... I mean it's not bad, an odd change especially considering doors still need to be on top of a solid block even if their hinges are connected to blocks, which is the more obvious requirement.... and iron doors spawn like that commonly in strongholds when the floor is deleted!

Rollback Post to RevisionRollBack

"I'm an outsider by choice, but not truly.
It’s the unpleasantness of the system that keeps me out.
I’d rather be in, in a good system. That’s where my discontent comes from:
being forced to choose to stay outside.
My advice: Just keep movin’ straight ahead.
Every now and then you find yourself in a different place."
-George Carlin